1. Field of the Invention
The present invention relates to a thermal treatment apparatus and a method for treating a fluid, the apparatus and method involving a fluidic device having a channel. In particular, the present invention relates to a method for regulating the transfer of a fluid in the channel during application of a temperature cycle.
2. Description of the Related Art
In analytical chemistry, desired data on, for example, concentration and components are generally obtained for confirmation of the progress and results of chemical and biochemical reactions, and various apparatuses and sensors have been therefore developed to obtain such data. Such apparatuses and sensors are formed in a reduced size by using a precision machining method and semiconductor-manufacturing equipment, and a technique called a micro total analysis system (μ-TAS) or a lab-on-a-chip has been developed. All processes for obtaining the desired data are performed on a micro device. In this technique, a collected unpurified specimen or a raw material is made to pass through a channel or micro space formed in a micro device to undergo, for instance, specimen purification or chemical reaction, thereby obtaining data on the concentration of a component contained in the final specimen or obtaining a chemical compound. These micro devices for such an analysis and reaction treat a minute amount of solution and gas and are thus often called a micro-fluidic device.
Use of the micro-fluidic device enables an amount of a fluid contained in the micro-fluidic device to be reduced as compared with existing desktop-size analytical equipment. It is therefore expected that the necessary amount of a reagent is decreased and that reaction time is reduced by virtue of decrease in the amount of an object to be analyzed. Technology associated with the μ-TAS has been developed with increasing appreciation of the advantages of the fluidic device.
However, the downsizing of the desktop-size equipment to the micro device generates new technical issues. For instance, a fluid confined in a micro channel becomes more sensitive to changes in environment. In particular, heat applied to the micro channel causes a fluid to be thermally expanded or evaporated, and these problems should be considered.
In the desktop-size equipment, since a micro tube or a well plate is used, a fluid content is thermally expanded in a substantially ignorable degree. In the micro channel, the fluid may be thermally expanded or evaporated to an undesirable degree. In order to suppress the transfer of a fluid, Japanese Patent Laid-Open No. 2008-151772 discloses a method in which heat is applied at a certain temperature to a micro channel that is in communication with a reaction field. By virtue of this method, even though a solution in the reaction field is partially evaporated with the result that the transfer of the solution is caused, the solution remains in a measurement region.
In addition to a method using the temperature adjustment, methods using a micro valve and a magnetic fluid have been proposed to suppress the transfer of a fluid. Furthermore, another method has been also proposed, in which the position of a solution in the channel is detected by taking an image and in which pressure from a pump that is in communication with the channel is then regulated to make the solution stay within a certain region (see Japanese Patent Laid-Open No. 2008-128906).
Although various techniques have been proposed to control a position of the fluid in the channel as described above, each technique has potential issues.
In particular, the device in which the micro valve is provided inside the channel needs a mechanism to control the opening and closing of the valve.
Furthermore, the method in which the magnetic fluid is put into the channel needs a mechanism to locally generate a magnetic field and is limited to the application in which the magnetic field does not prevent a reaction.
The technique which involves detecting the position of a fluid in an image and then regulating the pressure from a pump that is in communication with the channel increases the overall system cost. In addition, the accuracy of the position of the fluid depends on a feedback speed of the whole system.